1. Field
The present disclosure relates to a hydraulic oil deterioration ratio estimating apparatus in a vehicle.
2. Description of the Related Art
In general, engine oil used for lubricating the engine of a vehicle and hydraulic oil (ATF) used for lubricating a transmission of the vehicle deteriorates over time. Accordingly, the oil needs to be changed. Japanese Unexamined Patent Application Publication Nos. 2005-172048 and 2006-322587 describe existing technology for determining a deterioration level of ATF.
According to Japanese Unexamined Patent Application Publication No. 2005-172048, deterioration of ATF is caused by the following two factors: the temperature of ATF and the rotation speed. Thus, deterioration of ATF is detected using thermal deterioration based on the fluid temperature and mechanical deterioration based on the rotation speed, and an alert message is output.
According to Japanese Unexamined Patent Application Publication No. 2005-172048, if a fuel temperature sensor and a rotation sensor malfunctions, deterioration is estimated using a value output from the sensor that malfunctions. Thus, a significant error between an estimated deterioration value and a real deterioration value occurs. For example, if the fuel temperature sensor outputs a value lower than a real temperature, it may be determined from the estimated value that ATF is not deteriorated. In contrast, if the fuel temperature sensor outputs a value higher than the real temperature, it may be determined from the sensor value that the deterioration level is significantly high.
To address such an issue, according to the technology of Japanese Unexamined Patent Application Publication No. 2006-322587, it is determined whether a fuel temperature detection unit malfunctions. If the fuel temperature detection unit malfunctions, an alternative value of the fuel temperature is set, and a thermal deterioration ratio at a time of malfunction is calculated. Thus, the thermal deterioration ratio is accurately estimated. In addition, the alternative value is set to a value that is higher than the ATF temperature during normal running conditions of the vehicle by a predetermined value. Thus, the deterioration level is estimated in a fail-safe manner. Furthermore, malfunction of an engine speed detection unit, an input shaft rotation speed detection unit, and an output shaft rotation speed detection unit is detected. If malfunction of one of the detection units is detected, a mechanical ATF deterioration ratio is calculated by using an alternative value. In this manner, the ATF deterioration ratio is accurately estimated.